Ink jet images printed on the newer “instant dry” porous media generally suffer from fade or image loss caused by exposure to air pollutants. It has been shown in scientific literature that ozone exposure is the single most important factor of image loss. Images that are displayed unprotected, e.g., not framed, can show noticeable degradation in weeks or months. Current methods available to slow this degradation include protecting the image by framing it behind glass or placing it in a photo album. An alternate approach includes printing with colorants that are intrinsically stable toward ozone exposure.
Unfortunately ozone degradation is not the only source of fade or image loss. Light exposure may also contribute to image loss or fade to an inkjet image. Furthermore dyes that are both ozone stable and stable toward light exposure are difficult to manufacture and not easily available for purchase. For example azo dyes based on H-acid tend to be ozone stable, but very light unstable. On the other hand, azo dyes based on gamma-acid tend to be light stable, but very unstable to the effects of ozone. Additionally, Phthalocyanine dyes tend to be unstable toward ozone but light stable.
Various methods have been tried to improve ozone stability, such as adding sacrificial materials that remove ozone by chemical reaction. This solution is merely temporary, because once the sacrificial material is fully consumed by the chemical reaction the dyes will start to fade. Alternately, a few dyes have been found to have improved both light and ozone stability, but are still not as stable as would be desired. In some 3-color (e.g. cyan, magenta and yellow inks) printing systems one or more of the dyes used might have more ozone stability than the other(s) dyes. This can lead to color imbalance during image degradation which may result in the image being unacceptable before the dyes themselves had faded to an unacceptable level.